数据结构之二叉树：先中后序遍历（递归）

请用递归方式实现二叉树的先序、中序和后序的遍历打印。

给定一个二叉树的根结点root，请依次返回二叉树的先序，中序和后续遍历(二维数组的形式)。

代码：

*

struct TreeNode {

    int val;

    struct TreeNode *left;

    struct TreeNode *right;

    TreeNode(int x) :

            val(x), left(NULL), right(NULL) {

    }

};*/

 

classTreeToSequence {

public:

    vector<vector<int> > convert(TreeNode* root) {

        // write code here

        vector<int>vec2;

        vector<int>vec3;

        vector<int>vec4;

        vector<vector<int> >vec1;

        preOrder(vec2,root);

        midOrder(vec3,root);

        afOrder(vec4,root);

        vec1.push_back(vec2);

        vec1.push_back(vec3);

        vec1.push_back(vec4);

        returnvec1;

         

    }

    void preOrder(vector<int>&vec,TreeNode* root){

   

         if(root==NULL) return;

          

         vec.push_back(root->val);

         preOrder(vec,root->left);

         preOrder(vec,root->right);

          

    }

    void midOrder(vector<int>&vec,TreeNode* root){

         if(root==NULL) return;

                

         midOrder(vec,root->left);

         vec.push_back(root->val);

         midOrder(vec,root->right);

          

    }

    void afOrder(vector<int>&vec,TreeNode* root){

        if(root==NULL) return;

                 

        afOrder(vec,root->left);

        afOrder(vec,root->right);

        vec.push_back(root->val);

              

          

    }

};